warnings.catch_warnings() is only available on python 2.5

tests/presubmit_unittest.py

 #!/usr/bin/python
 # Copyright (c) 2006-2009 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Unit tests for presubmit_support.py and presubmit_canned_checks.py."""
 
 import os
 import StringIO
 import sys
 import unittest
 import warnings
 
 # Local imports
 import gcl
 import gclient
 import presubmit_support as presubmit
 import presubmit_canned_checks
 
 
 class PresubmitTestsBase(unittest.TestCase):
   """Setups and tear downs the mocks but doesn't test anything as-is."""
   def setUp(self):
-    self._warnings_stack = warnings.catch_warnings()
+    if hasattr(warnings, 'catch_warnings'):
+      self._warnings_stack = warnings.catch_warnings()
+    else:
+      self._warnings_stack = None
+    
     warnings.simplefilter("ignore", DeprecationWarning)
     self.original_IsFile = os.path.isfile
     def MockIsFile(f):
       dir = os.path.dirname(f)
       return dir.endswith('haspresubmit') or dir == ''
     os.path.isfile = MockIsFile
 
     self.original_CaptureSVNInfo = gclient.CaptureSVNInfo
     def MockCaptureSVNInfo(path):
       if path.count('notfound'):
@@ skipping 755 matching lines @@
     # TODO(maruel): Add real tests.
     self.failIf(presubmit_canned_checks.RunPythonUnitTests(
         self.MockInputApi(),
         presubmit.OutputApi, []))
     self.failUnless(presubmit_canned_checks.RunPythonUnitTests(
         self.MockInputApi(),
         presubmit.OutputApi, ['non_existent_module']))
 
 if __name__ == '__main__':
   unittest.main()